For the audiophile, the advent of FM stereo multiplexed broadcasting, and the growth of the industry in equipment for receiving such signals, has been a great boon. For many years the art has been aware of the greater realism of stereo sound reproduction as opposed to monaural reproduction. With the advent of stereo multiplexed transmission, a broadcasting station, using a single broadcasting channel, can now broadcast the two necessary signals for stereo sound reproduction. With the authorization of this type of broadcasting, the hi-fi industry has made available to consumers equipment necessary to receive and decode or demodulate this type of signal. In these receivers, as is the case generally in high fidelity sound reproduction equipment, a prime requirement is to maintain the signal to noise ratio such that sound reproduction is not disturbed by the presence of noise. There are a number of well-known techniques for maintaining adequate signal to noise ratio and thus assuring satisfactory sound reproduction.
On source of receiver distortion and noise which is particularly troublesome is termed multi-path, which is a short way of describing the phenomena in which the desired signal is received over at least two different paths and hence one arrives slightly later than the other. The delayed signal causes distortion and noise which must be suppressed.
The stereo decoder is particularly sensitive of any source of noise, and multi-path noise in particular, since the decoding process involves detecting a wider bandwidth than the bandwidth detected for mono reception and hence, the signal to noise ratio is reduced.